Pattern jack



Aug. 30, 1966 P. c. DAVIS 3,269,149

PATTERN JACK Original Filed Jan. 28, 1963 2 Sheets-5heet 1 Aug 30, 1966 P. c. DAVIS 3,269,149

PATTERN JACK Original Filed Jan. 28, 1963 2 Sheets-Sheet 2 Dax/i5; I ,im

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United States Patent O 3,269,149 PATTERN JACK Philip C. Davis, Laconia, N.H., assigner to Davis Tool Company, Incorporated, Laconia, N.H., a corporation of New Hampshire Original application Jan. 28, 1963, Ser. No. 254,266, now Patent No. 3,232,155, dated Feb. 1, 1966. Divided and this application June 11, 1965, Ser. No. 463,105 1 Claim. (Cl. 66-156) This invention relates to pattern jacks and similar parts used in knitting machines, for example machines which produce jacquard types of patterns. This application is a `division of my previous application Serial No. 254,266, iiled January 28, 1963, now Patent No. 3,232,155.

Pattern jacks of the type to which this invention relates are mounted in slots in the knitting head of a machine and are used to control the movement of the needles to produce various patterns. Typical jacks are made from uniform blanks of narrow strip shape originally equipped with a number of `teeth yalong one edge. All but a selected number of teeth are cut oli on each blank `and the remaining teeth engage cams which operate the needles. The positions of the selected teeth in a sequence of jacks deter-mines the pattern which will be produced. The jacks are bent at various points to lit certain positions in the knitting head. In ope-ration the teeth are subject both to wear along -their top edge and to shear stress in the longitudinal Idirection of the blank.

The jack blanks are customarily made from hardened rolled vsteel which has a characteristic grain structure lying parallel to the direction of rolling. The she-ar strength of this material, along the grain, is Iappreciably lower than the shear strength across, or perpendicular to, the grain. The wear resistance of an edge cut across the grain is greater than that of an edge cut parallel to the grain. Finally, the material holds a `bend well when bent around `an axis perpendicular to the grain and poorly when bent around an axis parallel to the grain.

According to previous practice, jack blanks are punched from a narrow strip wit-h the longitudinal direction of the blank lying parallel to that of the strip and to the grain. Jacks cut in this manner have good bend retention in the desired direction, that is around axes transverse to the blank. The teeth have relatively poor shear strength, however, because they are subject to shear stress in the longitudinal direction of the blank, which corresponds to the grain direction. As a result, the teeth sometimes fbreak.

When punching blanks longitudinally from a strip, a certain margin of waste material must be left on each side for proper punching action. Furthermore, 'for proper operation and maximum wear resistance on the top edges which engage the cams, the teeth should have square ends. As it lis ydilcult to machine and maintain sharp `corners on dies `and punches adapted to cut the rather fine teeth, the blanks are usually punched in two operations, by forming the blank and then cutting slots to form the teeth.

The principal object of this invention is to produce a pattern jack having adequate bend retention characteristics in the desired direction, and in which the teeth have both high shear strength and good edge wear resistance.

The improved pattern jack here shown is punched obliquely from a strip of stock, so that the grain is oblique to the longitudinal direction of the jack and to the teeth. The teeth thus have both good wear resistance at their top and side edges and high shear strength in the longitudinal direction. The blank also has good .bend retention characteristics. According to the improved method of production, the strip is fed to the punching `'die at an 3,269,149 Patented August 30, 196

oblique angle. The die cavity has tooth forming slots and the punch has corresponding teeth, somewhat longer than the finished length of the jack teeth. The straight edge left in the stock by punching out the rear edge of one jack blank is laid on the die partway over the slots and becomes the ends of the teeth of the next blank. Teeth of the desired square ended shape are thus produced in one oper-ation.

In the drawings illustrating the invention:

FIG. 1 is a plan view of a piece of stock from which several jack blanks have been punched out according to the meth od here disclosed;

FIG. 2 is a schematic plan view, partly broken away, of the stock in position over a die for punching la blank;

FIG. 3 is an enlarged plan view of a finished jack blank;

FIG. 4 is an enlarged view, taken in the direction of line =t-4 of FIG. 3, showing a jack blank bent to a typical form;

FIG. 5 is an enlarged fragmentary prospective view of a punch yand die used in the method; and

FIG. 6 is a cross-section, somewhat reduced in scale, taken along line 6-6 of FIG. 5, showing the stock in place to be punched.

The jack blank generally indicated by the numeral 10 shown in FIG. 3, has a straight rear edge portion 11, a lower end portion 12 having a rear edge 13 somewhat oblique to edge portion 11, and upper end portion 14, and a number of teeth 15 with square cut ends 15a. The grain of the rolled hardened steel stock from which the jack is marde lies -obliquely to the end-to-end direction of the jack, the direction of the grain being indicated by arrow 16.

In FIG. 1 a typical strip 17 of the rolled steel stock is illustrated. As is customary, the grain runs in the longitudinal direction of the strip, as indicated by arrows 18. Several jack blanks have been cut from the lower portion of the strip at an oblique angle. The -last blank cut out leaves a .straight edge portion 19 and an edge portion 20 slightly oblique to 19. These edge portions correspond to rear edge portions 11 and 13, respectively, of the jack just cutout.

The outline of the next blank to be cut from the strip is indicated by the ydotted line 21. The jack blanks are cut from the strip 17 by means of a die 22 having a cavity 23, and a sheet metal punch 24 having a conguration mating with the die cavity. The cavity has slots 25 which receive corresponding teeth 26 on the punch yfor cutting out the jack teeth. The slots and corresponding punch teeth are deeper than the desired length of the teeth on the jacks. The strip 17 is positioned on the die at an angle oblique to the longitudinal direction of the cavity 23, and is placed so that the straight edge 19, left by cutting the previous blank lies partway over slots 25, for example in line 29 of FIG. 5, leaving the bases 25a of the slots exposed. In this manner, teeth with square ends are cut in the jack, even though bases of slots 25a, and the corresponding ends 26a of the punch teeth are made with rounded corners for better wear and ease of machining. The bases of the slots and the end portion of the teeth which project beyond the position of the edge of the stock need not `mate precisely because the punch and die do not perform any cutting in this region. Indexing holes 27, spaced to correspond to the blank dimension in the direction of the strip, may be punched along the side margins of the strip in any suitable manner, and engaged successively by pins 28 on the die to align the strip `in the correct position for each punching operation.

For obtaining the optimum combination of shear strength and top edge wear on lthe teeth, it is preferable to punch pattern jacks at an angle of 45 to the longitudinal direction or grain direction of the strip of stock. At

this angle, the jack has satisfactory bend retention characteristics when bent for use in a knitting machine, as exemplified in FIG. 4. The amount to which the angle of the jack to the grain may be reduced below 45 is limited by geometric considerations, because beyond a certain point the ends of the right-hand teeth would fall on edge 20. For a typical four inch jack having a straight edge 11 about three inches long, the lower angle limit is about 20. A smaller angle down to about 10, for example, where the conguration of the jack permits, would still give some improvement in the shear strength of the teeth as compared to jacks cut parallel to the grain of the strip in the usual manner.v

As the angle of the jack to the strip is increased from 45 toward 90, or across the grain, the edge Wear resistance of the teeth and the bend retention characteristics are both decreased.

A pattern jack punched at an angle to the grain, as here described, is `superior to previous jacks from the standpoint of shear strength of the teeth and yet has adequate wear resistance and ability to retain bends.

It is understood the method here described may be used to produce selector jacks, needles and other parts which are customarily punched from ilat stock and have portions which, like the teeth of a jack, have to be cut to a square-edged configuration. The term pattern jack, as used herein, is intended to include similar parts.

What is claimed is:

A pattern jack for knitting machines comprising an elongated body portion having a longitudinal direction, teeth yprojecting laterally from said body portion, the jack being formed of sheet metal of a type having a grain structure imparting a shear strength perpendicular to the grain higher than that parallel to the grain, and the grain being disposed at an angle of approximately 45 with respect to said longitudinal direction.

References Cited by the Examiner UNITED STATES PATENTS 1,339,990 5/1920 Troy 83-36 1,780,328 11/1930 Ames 66-156 2,209,529 7/1940 Lawson 66--50 MERVIN STEIN, Primary Examiner.

DONALD W. PARKER, P. C. FAW,

Assistant Examiners. 

